According to the National Fire Prevention Association, in the United States in 2000, a residential fire occurred every 83 seconds (www.nfpa.org). These fires have the potential to affect, displace, or injure thousands of people a day. And over thirty-four hundred people died in these fires. The fires also caused over five billion dollars in property loss, resulting in over four billion dollars paid by the insurance industry under homeowner's insurance policies. (Insurance Information Institute, New York, N.Y., www.iii.org).
Often, a homeowner can prevent a fire from occurring. In the fires that cannot be prevented, the homeowner can take steps to minimize the consequences. One way in which a homeowner can minimize any damage that may occur is to install a smoke, heat, carbon monoxide, or other detector. The detector warns the occupants, and perhaps a security agency, that the conditions present in a fire are occurring so that the homeowner can undertake the proper response, such as contacting the fire department, extinguishing the fire, and leaving the residence.
Unfortunately, simply notifying the homeowner or security agency that a rapidly progressing fire is occurring may not be enough to save the life of the homeowner or to avoid damage to the house. A fire needs time to develop. In many cases, a residential fire initially emits relatively little heat and exhausts the supply of combustion air in a room in a residence very quickly. Unfortunately, even a relatively low-temperature fire quickly raises the temperature of a room by several degrees. When the temperature rises, the thermostat may trigger the heating, ventilation, and air conditioning (HVAC) system fan to start, forcing air into the room and providing combustion air necessary for the fire to grow and spread. In conventional homes, this progression of the fire stops only when the power fails, which usually only occurs after the fire department removes the power company's meter.
A similar situation occurs in large commercial buildings. Often, in a commercial building, heat or smoke detectors are connected to a heating ventilation and air conditioning (HVAC) system. When the detectors indicate that the environmental conditions of a fire are present, the detectors or a master controller signal the HVAC system to cease functioning or to close the air ducts feeding air to the specific parts of the building from which the warning is emanating. These air ducts are normally used to control the distribution of air in order to control the temperature in various parts of the building. The ability to use them to starve a fire of combustion air is a fortunate consequence of their installation. See, e.g., U.S. Pat. No. 5,945,924. Unfortunately, the types of duct control mechanisms used by conventional commercial HVAC systems are not present in residential HVAC systems. Conventionally, systems such as these are not required unless a building requires an HVAC system providing a heating and cooling capacity of at least five tons per unit.
Large commercial buildings may include other mechanisms for suppressing or extinguishing a fire. For example, many commercial buildings include sprinkler systems. Also, the computer rooms of a business may include a halon system to deprive a fire of combustion air. These systems are rarely present in residential buildings.
Another threat posed to commercial and residential building alike is the danger of a biochemical hazard, such as mold or anthrax, spreading through a building. In conventional large commercial buildings, a detector designed to detect specific biological materials can be integrated into the same controls used for the suppression of fire. This type of safeguard is not present in conventional residential and small commercial buildings.
Conventional residential and small commercial buildings have relatively simple HVAC systems. Generally, one or two compressors cool a liquid contained in tubing over which air is forced by a fan. These systems are called forced air systems. The cooled air then passes through ducts and out various registers located throughout the residence. The registers may be closed manually, but conventional residential HVAC systems do not include automated mechanisms for closing individual ducts or registers. Therefore, no conventional mechanism exists for suppressing fire by shutting off the air supply in a residence.